A fuel cell comprises an electrolyte layer and a pair of electrodes placed on either side of the electrolyte layer, and generates electricity through an electrochemical reaction between fuel gas such as hydrogen and alcohol and oxidizing gas such as oxygen and air, which are supplied to the corresponding electrodes, with the aid of a catalyst. There are a number of different types of fuel cells that have been proposed. Many of them use liquid electrolytes, but those using solid electrolytes are being preferred more and more for the ease of fabrication and handling.
However, the voltage output produced from each cell is very low, typically in the order of 1 volt or less, and most applications require substantially higher voltages. Therefore, it is necessary to connect individual fuel cells electrically in series or stack a number of individual fuel cells. In either case, the fabrication process gets complicated, and the fabrication cost increases. Also, it is not easy to ensure proper electric insulation between individual fuel cells, and reduce the internal resistance of the electrical path in the fuel cell assembly.
Conventionally, because of the need to form fuel and oxidant passages for a number of fuel cells of an assembly, there has been some difficulty in achieving a compact design of a fuel cell assembly. In particularly, previously proposed fuel cells typically had stacked structures, and this necessitated a certain dimension in the stacking direction. However, in some applications, it is desirable to provide a fuel cell assembly in the form of a sheet.